Switch



Defiv 1956 H. .J. CROMWELL 2,773,958

SWITCH Filed Oct. 8, 1955 Z6 .5ucT/o/v 5W, MOTOR United States Patent-OSWITCH Harold J. Cromwell, Anderson, Ind., assignor to General MotorsCorporation, Detroit, Mich., a corporation of Delaware ApplicationOctober 8, 1953, Serial No. 384,834

2 Claims. (Cl. 200-83) This invention relates to electric switches andis particularly concerned with vacuum actuated electric switches.

An object of the invention is to provide a vacuum operated electricswitch which is biased to closed circuit position under a predeterminedload and which includes a vacuum operated device capable of overcomingthe bias and opening the switch under predetermined conditions ofvacuum, means being provided for reestablishing the switch in closedcircuit position after a predetermined time delay upon the eliminationof the vacuum.

A further object of the invention is to provide a switch for use in anelectrical system of an automotive vehicle wherein a safety switch isprovided in the starter circuit, which switch is normally closed andwhich is opened by a vacuum actuator upon starting of the engine, saidswitch being designed so as to provide a time delay for preventingrestarting of the engine until such time that the engine has ceased torotate.

In automotive starting systems, a starter switch is generally providedwhich, upon closure, energizes the starter. Engine starters ofconventional design include means for engaging the starting motor withthe flywheel of the engine through suitable gears and disengaging themotor from the flywheel of the engine after the engine has been started.In many instances, when false starts are encountered, the engine ceasesto function shortly after starting and the operator of the vehicle mayreclose the starter switch prior to the time that the engine has stoppedrotating. Under these conditions, the starter motor is again thrown intoengagement with the flywheel. This condition frequently causes breakingof some of the flywheel teeth, since the flywheel is still moving at thetime the starter is energized and proper engagement of the gears is thusprevented. It is, therefore, highly desirable to prevent energization ofthe starting motor prior to the time that the engine has stoppedrotating.

Not only is this provision useful in case of false starts but it is alsouseful during operation of the engine, when, due to silent operation,the operator closes the starter circuit when the engine is runningthereby causing engagement of the starter motor gears 'w ith theflywheel gear at the time the flywheel is in rotation which againcreates a condition where gear teeth may be broken ofi. Therefore, it isparticularly desirable in engine starting systems to provide means forpreventing energization of the starting motor during any period that theengine is rotating. The present invention is specifically directed tosolving this problem in an inexpensive and highly etiective mannerthrough the use of a novel vacuum operated switch placed in series withthe starter motor, or device which actuates the starting motor.

Further objects and advantages of the present invention will be apparentfrom the following description reference being had to the accompanyingdrawings wherein a preferred embodiment of the present invention isclearly shown.

2,773,958 Patented Dec. 11, 1 956 In the drawing: 1

Fig. 1 is a plan view of a vacuum switch.

Fig. 2 is a section taken on line 22 of Fig. 1, showing the internalstructure of the switch.

Fig. 3 is a diagrammatic electrical hookup of a starter motor used inconnection with an internal combustion engine.

Referring specifically to Fig. 2, a switch 20 is shown which includes abase plate 22 of insulating material having two contacts 24 and 26carried thereby. These contacts are bridged by a spring bridging member28 spring-pressed against the contacts by means of a spring 30.Interposed between the spring 30 and the contact member 28 is a flexiblediaphragm 32 held peripherally between two casing members 34 and 36which are also engaged with the base plate 22. The spring 30 surroundsand is carried by a downwardly extending tube 38 attached to the uppercasing member 36. Within the tube 38 is a ferrule 40 having a passage 41therethrough which is closed by a ball 42 that is spring-pressed againstthe aperture at the end of passage 41 in the ferrule 40 by a smallspring 44. The outer end of the tube 38 is ap'ertured as at 46.

The spring bridging member 28 is insulatedly carried by a centrallylocated plunger 48 which passes through and is journalled in the baseplate 22 and which includes a pair of grooves 50 and 52 therearound.These grooves are adapted to be engaged by a ball 54 spring-pressed byspring 56 into engagement with one or the other of the grooves 50 or 52.The ball and spring are held within a transverse cavity in the baseplate 22. This structure acts as a yieldable detent for the plunger 48spring contact member 28 whereby the spring contact member is maintainedin either open or closed position under a certain predeterminedresisting pressure as determined by the detent.

In the upper casing member 36 is placed a vent 58 which is opened to theatmosphere at 60 and opened to the inside of the casing member 36through a small aperture 62. Within the vent 58 is fibrous material 64which acts as a filter and restrictor to prevent ingress of dirt andclogging of the small aperture 62.

In operation of the device, a flexible tube (not shown) is attached tothe upper end of the tube 38 so as to communicate with the aperture 46therein. The spring 30 normally presses the diaphragm 32 in the positionshown in Fig. 2, and thereby maintains the spring bridging member 28 inclosed circuit position with respect to contacts 24 and 26. The flexibletube, not shown attached to the tube 38, is attached at its opposite endto an intake manifold and upon creation of vacuum therein, causes theball 42, which in reality is a check valve, to open and thereby drawsair out of the upper chamber of the casing 36 above the diaphragm. Whenthe vacuum within the chamber 36 is sufficient, the diaphragm 32 isdrawn upwardly to cause the bridging member 28 to open circuit contacts24 and 26. The vacuum in the intake manifold is sufficient to overcomethe slight leakage into the chamber 36 through the reduced diameterorifice 62 so that as long as the engine is in operation, the diaphragm32 is held under vacuum in a position to maintain the bridging member 28in switch opening position. The detent 52 aids in yieldably maintainingthe switch in open position.

When the engine ceases to operate, the vacuum in the intake manifolddrops oif rapidly and when the engine stops, there is no vacuum withinthe intake manifold which is then at atmospheric pressure. The switch,how ever, does not close until the interior of casing 36 isreestablished at substantially atmospheric pressure due to bleeding inof outside air through the reduced orifice 62. The size of the orificedetermines the time delay. Thus,

3 after a predetermined time delay, the pressure within the casing 36 isbuilt up so that the spring 30 overcomes the detent 52 to again closethe switch by closing the bridging member 28 to engage both contacts 24and 26.

In the installation of this switch, a hookup as shown in Fig. 3 may beused wherein 70 is .a starter motor, 72 is a starter switch and 74 is abattery. The battery 74 and the motor 70 are both grounded at one sidethereof. The switch 20 is placed in series with the starting switch andis normally closed. When the starter switch 72 is closed, current isimmediately impressed upon the motor 70 to cause the same to rotate andcause the starter driving mechanism to engage the flywheel of theengine. As soon as the engine is started, vacuum is established withinthe manifold which effects the pressure conditions within the casing 36of the switch 21). After a very short time delay as caused by buildingup vacuum in the casing 36 sufiicient to overcome the resistance of thedetent 50 and spring 30 whereupon switch 20 opens to cause the startermotor to become deenergized. After the engine fails to continue tooperate due to a false start, it is impossible to reclose the startermotor circuit through switch 72 until such time as the vacuum within thechamber 36 is substantially destroyed due to air being admitted throughthe metering orifice 62. Since this orifice is small suificient timedelay is created before the switch 20 is reclosed to assure that theengine has stopped rotating whereupon the starter switch '72 may bereclosed and the cycle re peated.

The system also prevents the engagement of the starter with the flywheelduring normal operation of the system since the switch 20 is in opencircuit position at all times during normal operation of the internalcombustion engine.

It will thus be seen that the switch 20 acts as a safeguard againstinjury to the flywheel or starter motor drive gear since it preventsengagement of the starter motor gear with the flywheel gear during anytime that the internal combuston engine is rotating. This action isassured by the definite and predetermined time delay before the switch20 is placed in closed circuit position after the engine ceases tooperate. it is manifest that this switch is of an inexpensive design,yet is fully capable of controlling the circuit as outlined. The switchis simple in construction and has a minimum of moving parts.

The description of the vacuum switch in a starter system, as notedherein, relates to a simplified hookup. In many instances, the startermotor is placed in circuit through a relay or solenoid switch whereinthe starter switch per se actually closes the circuit to the solenoidwhich, in turn, closes a switch for the starter motor circuit.Obviously, the vacuum switch, as noted herein, is capable of use in sucha circuit wherein its operation determines the opening or closing of thecircuit to the solenoid coil rather than to the starter per se. solenoidsetup is clearly shown in Dyer Patent #2,167,646.

It is apparent that the switch may also be used in any applicationwherein vacuum is created during operation of a device and wherein timedelay is desired before a circuit can be energized after the destructionof the vacuum.

Such a While the embodiment of the present invention as herein disclosedconstitutes a preferred form, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

1. A vacuum switch comprising, in combination, a pair of contacts, abridging member, a chamber closed by a diaphragm, a spring within saidchamber normally causing said diaphragm to be moved to one position,means connecting the diaphragm to the bridging member whereby thebridging member is held in closed circuit position when said diaphragmis in said'one position, a normally closed check valve communicatingwith said closed chamber means adapted to connect the closed chamberwith a vacuum source through said check valve whereby the check valve isopened only under predetermined conditions of vacuum and the diaphragmis moved to another position for causing said bridging member to bemoved to open circuit position when said predetermined vacuum isapplied, and'detent means associated with said bridging member for andan independent bleed valve connecting said closed chamber to theatmosphere for permitting the spring to re-establish the bridging memberin closed circuit position after the vacuum has been destroyed and onlyafter a predetermined time delay as determined by the bleed valve.

2. A vacuum switch comprising in combination; a closed chamber, adiaphragm disposed in said chamber so as to divide the chamberinto twoindependent compartments, switch means in one of said compartments, aslidable support for said switch means operatively connected to saiddiaphragm and movable to two extreme positions whereby said switch meansare caused to be moved to open or closed position, means for yieldablyresisting movement of said support from either of said two positions,means in the other of said compartments for normally biasing saiddiaphragm and said supportin one direction, a normally closed checkvalve providing an entry in said other compartment and adapted to beconnected to a source of vacuum whereby said valve is opened said othercompartment is evacuated only upon a predetermined vacuum beingimpressed upon said valve for causing said diaphragm and support to moveagainst the biasing means and to overcome the means for yieldablyresisting movement for actuating the switch means, a second valve meansin said compartment including a restricted opening independent of saidvalve for permitting reestablishment of the diaphragm and support to aposition in said one position after the vacuum has been destroyedthrough the action of said biasing means and only after a predeterminedtime delay as determined by the size of said opening.

References Cited in the file of this patent UNITED STATESPATENTS1,984,736 Garoutte .Dec. 18, 1934 2,007,058 Maurer. July 2, 19352,024,619 Whitney Dec. 17, 1935 2,632,119 Schneider et a1 Mar. 17, 19532,654,036 Schneider et al Sept. 29, 1953

